The ecdysis behaviors of moths provide a model system in which the action of a peptide hormone in altering behavior can be examined. The isolated CNS from this insect responds to defined peptide cues by performing a stereotyped motor program as well as activating specific reflexes. In the case of one reflex, the neural pathway has been worked out and the site of action of the peptide has been localized to the interneuron-motoneuron synapse. Proposed work will involve examination of the changes that occur at this synapse in response to the peptide. Also we will continue our neural analysis of some of the other behaviors activated by the peptide. Work is also in progress to radioactively label the peptide so that it can be used as a probe to find putative target cells. Also, some of the early biochemical actions of the peptide on the nervous system are under study. These include the changes in cyclic GMP and calcium concentrations after peptide exposure.